The need for the use of heat shields has greatly increased in motor vehicles. This is essentially caused by the fact that the space available in the engine compartments of motor vehicles has to be exploited to the maximum in order to accommodate the assemblies, components and connection lines necessary for operation, such that these parts have to be arranged very close to one another. This leads to heat-sensitive components having to be arranged very close to very hot components, such as for example the exhaust system, the combustion engine or the heat exchanger. The heat radiated by these elements can adversely affect the functioning of the heat-sensitive components. To this end, the heat-sensitive elements or components are protected from the heat radiation and the high temperatures by heat shields arranged in front of them.
DE 38 34 054 C2 discloses a heat shield, in which, in order to protect from heat radiation, at least two flat materials are used which are connected to one another on at least two edge regions turned away from one another. The flat materials mentioned are connected to one another in such a way that a gap is formed between them. Moreover, with this known heat shield it is important that the flat material facing the source of the heat radiation is so oriented in its expansion characteristic by pre-determined profiling or beading or corresponding choice of material that it expands towards the heat source. Through corresponding configuration, adaptation to the heat load arising should be made possible, since with higher temperatures the spacing of the two flat materials used, which should preferably consist of sheet metal is increased and an enlarged air gap is produced which naturally improves the insulation effect.
The heat shield described in DE 38 34 054 C2 can then be further improved in relation to its insulating effect if a heat insulation layer is applied in addition to the inner surfaces of the flat materials proposed there. Suitable insulating materials may include organic or inorganic fibre materials, but also metallic woven fabrics, knitted fabrics or expanded metals (grids), which are also intended to improve the soundproofing.
The heat shield described therein has a substantial disadvantage in the fact that it is not possible for every conceivable contour of the heat shield to be configured to achieve the desired effect for adaptation to the different temperatures.
Moreover, the insulation effect is limited if only an air gap is used without additional heat-insulating materials.
If on the other hand, as explained already, heat-insulating layers are applied, then in return increased manufacturing outlay is incurred. For the application of the heat-insulating materials as a heat-insulating layer, binding agents are necessary.
However, such binding agents generally have organic components which cause problems at the high temperatures.
Furthermore, in DE 39 05 871 C2, a compound material for heat insulation and sound proofing for screening parts and heat shields in the automobile field are described. An insulation layer, consisting of a thermally resistant highly porous inorganic material is used which is enclosed on at least one side with a stabilising, structurally fixed covering layer, preferably a metal foil. This covering layer surrounds the insulation layer in one example completely, or, in the case where the compound material, formed from an insulation layer and the covering layer, is disposed on the surface of a screening part, on the side turned away from the surface of the screening part.
For the insulation layer, various inorganic materials are mentioned which are preferably foamable (water glass, foamed glass, glass concrete, foamed ceramic or clay mineral materials) and thermally resistant reinforcing fibres or flakes (mica or graphite). The insulation layer of the compound material described there should be manufactured by foaming of a suitable material. The foamed material is then surrounded with the covering layer already mentioned. Here, besides the relatively high manufacturing outlay, what has proved disadvantageous is that the foamed material has, after it has hardened, a specific shape which can only be altered slightly or with additional outlay. This leads to problems and to increased technological outlay in the manufacture of heat shields, when more complicated shapes are necessary for same.
DE 39 05 871 C2 discloses a concept of adding thermally resistant fibres or flakes (mica or graphite) to the actual insulation layer material. Such fibres or flakes are intended to improve in particular the mechanical properties.
A further disadvantage of heat shields manufactured according to this theory consists in the fact, that greater forces acting on these heat shields can lead to deformations, or even to rupturing of the insulation layer material. This can lead to impairment of the actual functioning, and in conjunction with vibrations, to noise.
Moreover, it must be guaranteed that the composite material described in DE 39 05 871 C2 is surrounded by outer covering layers and a connection with the screening part must be ensured, which prevents vibrations occurring which can lead to annoyance caused by noise.
Proceeding from the above, an object of the present invention is to propose a method and a heat shield manufactured with this method, the method being intended to be simple and able to be carried out at a favourable cost, and the heat shield manufactured with this method being safe from a toxicological and ecological point of view.